Objective:

Chloroethenes are among the most common groundwater pollutants in the country. Natural attenuation of chloroethenes in anaerobic systems often leads to an accumulation of vinyl chloride, a proven human carcinogen. Currently chloroethenes are difficult and expensive to remediate. However, several species of bacteria have been discovered that are capable of degrading chloroethenes, and the most promising among these is Dehalococcoides because it is the only known bacterium capable of complete, metabolic dechlorination to non-toxic ethene. This project will attempt to better explain how this unique bacterium functions in the environment and the extent to which it can be exploited for bioremediation.

The objective of this project is to better understand the biology of reductive dechlorination, particularly at sites of subsurface chloroethene contamination and the unique role of the anaerobic bacterium Dehalococcoides. Results of this work will contribute to the development of a standard set of molecular tools that remediators can use to guide their clean-up strategies. Furthermore, it appears that some strains of Dehalococcoides are capable of dechlorinating other important environmental contaminants, such as dioxins and PCBs. A secondary objective this project is to identify additional compounds that can act as respiratory substrates for Dehalococcoides, and determine the genes involved.

Approach:

I propose a combination of computational, molecular, and microbiological methods to better characterize reductive dechlorination in the environment. This includes annotation and analysis of a pending genome sequence of Dehalococcoides strain VS, as well as analysis of laboratory-scale soil-packed bioreactor columns that simulate in-situ conditions.

Expected Results:

A preliminary round of experiments on laboratory-scale soil-packed bioreactors is nearly complete and provides a basis for predicting further results of this project. The next several rounds of soil column tests will produce useful information about remediation parameters, such as the concentrations of electron donor required to effectively support in-situ bioremediation, the effectiveness of bioaugmentation, and so on. Optimization of molecular tools for site characterization is also an expected result of this work.

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.